IFNG and neoplasm: Thus, tumor cells indirectly inhibit the functionality of NK cells by producing lactic acid.260 In an immunogenic mouse model of melanoma, tumors that produced less lactic acid developed at a significantly slower rate than the control group, and a greater number of IFN-γ+ NK cells infiltrated the tumor sites.261 This indicates that lactic acid may also inhibit the invasion of NK cells into the TME.